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RE: Nonces/hashes in source expressions.

From: Hill, Brad <bhill@paypal-inc.com>
Date: Mon, 18 Mar 2013 17:23:40 +0000
To: Mike West <mkwst@google.com>
CC: "dveditz@mozilla.com" <dveditz@mozilla.com>, "public-webappsec@w3.org" <public-webappsec@w3.org>, Adam Barth <w3c@adambarth.com>
Message-ID: <370C9BEB4DD6154FA963E2F79ADC6F2E279694B3@DEN-EXDDA-S12.corp.ebay.com>
I suppose that is narrowly true, but we do allow in 1.0 that it is OK to supply additional path information which will be truncated.  If that additional information includes a (valid in many URL schemes) ';' character, it must be properly encoded.

From: Mike West [mailto:mkwst@google.com]
Sent: Monday, March 18, 2013 11:21 AM
To: Hill, Brad
Cc: dveditz@mozilla.com; public-webappsec@w3.org; Adam Barth
Subject: Re: Nonces/hashes in source expressions.

1.0 supports neither paths nor nonces. Which values are you concerned about?

-mike

--
Mike West <mkwst@google.com<mailto:mkwst@google.com>>, Developer Advocate
Google Germany GmbH, Dienerstrasse 12, 80331 München, Germany
Google+: https://mkw.st/+, Twitter: @mikewest, Cell: +49 162 10 255 91

On Mon, Mar 18, 2013 at 6:19 PM, Hill, Brad <bhill@paypal-inc.com<mailto:bhill@paypal-inc.com>> wrote:
Given that it is a valid character in use at least some places that might show up as directive values, I think encoding is a better answer.

I don't think requiring the additional encoding is a problem, but this is probably something we also need to address in the 1.0 CR draft.

From: Mike West [mailto:mkwst@google.com<mailto:mkwst@google.com>]
Sent: Monday, March 18, 2013 11:13 AM

To: Hill, Brad
Cc: dveditz@mozilla.com<mailto:dveditz@mozilla.com>; public-webappsec@w3.org<mailto:public-webappsec@w3.org>; Adam Barth
Subject: Re: Nonces/hashes in source expressions.

We currently just define the grammar such that ';' can't appear in a directive's value: see section 3.2.1 (https://dvcs.w3.org/hg/content-security-policy/raw-file/tip/csp-specification.dev.html#policies).

The only place this might be worrisome at the moment is nonce and URL paths. I don't have a problem with excluding ';' from the valid nonce characters, nor with asking developers to percent-encode ';' as '%3B'. Would that sufficiently address the problem, or is there something deeper I'm missing?

-mike

--
Mike West <mkwst@google.com<mailto:mkwst@google.com>>, Developer Advocate
Google Germany GmbH, Dienerstrasse 12, 80331 München, Germany
Google+: https://mkw.st/+, Twitter: @mikewest, Cell: +49 162 10 255 91<tel:%2B49%20162%2010%20255%2091>

On Mon, Mar 18, 2013 at 6:06 PM, Hill, Brad <bhill@paypal-inc.com<mailto:bhill@paypal-inc.com>> wrote:
A twitter follower pointed out this is also in data URIs.  How do we deal with this?

(time to get back to working on tests now that IETF is over...)

> -----Original Message-----
> From: Hill, Brad
> Sent: Monday, March 18, 2013 10:44 AM
> To: Hill, Brad; Mike West
> Cc: dveditz@mozilla.com<mailto:dveditz@mozilla.com>; public-webappsec@w3.org<mailto:public-webappsec@w3.org>; Adam Barth
> Subject: RE: Nonces/hashes in source expressions.
>
> I seem to recall that Tomcat uses the ';' to do URL rewriting for session
> management.  Not a secure practice, but certainly popular in the 90's.
>
> > -----Original Message-----
> > From: Hill, Brad [mailto:bhill@paypal-inc.com<mailto:bhill@paypal-inc.com>]
> > Sent: Monday, March 18, 2013 10:39 AM
> > To: Mike West
> > Cc: dveditz@mozilla.com<mailto:dveditz@mozilla.com>; public-webappsec@w3.org<mailto:public-webappsec@w3.org>; Adam Barth
> > Subject: RE: Nonces/hashes in source expressions.
> >
> > Eww.. yes.   But that does point out a potential problem more generally in
> CSP:
> >
> > According to RFC3986 section 2.2, ';' is a reserved character as a
> > subcomponent delimiter.
> >
> > Is this going to bite us elsewhere?
> >
> > :(
> >
> > -Brad Hill
> >
> > ---------------------
> > From: Mike West [mailto:mkwst@google.com<mailto:mkwst@google.com>]
> > Sent: Monday, March 18, 2013 10:35 AM
> > To: Hill, Brad
> > Cc: dveditz@mozilla.com<mailto:dveditz@mozilla.com>; public-webappsec@w3.org<mailto:public-webappsec@w3.org>; Adam Barth
> > Subject: RE: Nonces/hashes in source expressions.
> >
> > One more observation: we can currently safely assume that ';'
> > separates directives. We could no longer make that assumption with
> > this format, which would make parsing slightly more complicated.
> > -mike
> > On Mar 18, 2013 5:31 PM, "Mike West" <mkwst@google.com<mailto:mkwst@google.com>> wrote:
> > Thanks for the link, it's very informative. The only reservation I
> > have is that it seems to imply a 1:1 relationship between the URL and
> > the resource being described (modulo collisions). Nonces are meant to
> > collide, probably multiple times on a single page.
> > That said, I don't feel strongly about the format. I'd be happy to
> > adopt that format wholesale, assuming the general idea (which, the
> > more I think about, the more strongly I favor) is acceptable.
> > -mike
> > On Mar 18, 2013 5:19 PM, "Hill, Brad" <bhill@paypal-inc.com<mailto:bhill@paypal-inc.com>> wrote:
> > <hat type="individual">
> >
> > I like it.
> >
> > </hat>
> >
> > <hat type="chair">
> >
> > This draft is relevant to consider vs. inventing a new identifier
> > syntax, though it is less compact than what you suggest:
> >
> > http://tools.ietf.org/html/draft-farrell-decade-ni-10
> >
> > </hat>
> >
> > Brad Hill
> >
> > -------------------------
> > From: Mike West [mailto:mkwst@google.com<mailto:mkwst@google.com>]
> > Sent: Monday, March 18, 2013 10:04 AM
> > To: public-webappsec@w3.org<mailto:public-webappsec@w3.org>; dveditz@mozilla.com<mailto:dveditz@mozilla.com>; Adam Barth
> > Subject: Nonces/hashes in source expressions.
> >
> > Before I copy/paste a bunch of text to stub out a 'style-nonce'
> > directive for CSP 1.1, I'd like to run something by you lovely folks
> > that I think we've talked about once or twice on the calls. It seems
> > like it could reduce repetition and confusion if we fold nonces or
> > hashes into the existing directives as another type of source expression.
> >
> > As a strawman, how would you feel about rewriting 'script-nonce
> > ABCDEFG' as 'script-src nonce:ABCDEFG'? This would make an "or"
> > relationship with 'script- src' clear on the one hand, and make room
> > for something like 'script-src sha1:...' on the other. I think it
> > would simplify the structure in a nice way, and seems more comprehensible
> and reusable in general.
> >
> > I'm sure others of you will have ideas about syntax (perhaps it's a
> > bad idea to replicate scheme-like structures... maybe '#' would be a
> > better separator, since it's sometimes read as "hash" anyway), but I'm
> > hoping the general idea is reasonable.
> >
> >
> > --
> > Mike West <mkwst@google.com<mailto:mkwst@google.com>>, Developer Advocate Google Germany
> GmbH,
> > Dienerstrasse 12, 80331 München, Germany
> > Google+: https://mkw.st/+, Twitter: @mikewest, Cell: +49 162 10 255 91<tel:%2B49%20162%2010%20255%2091>
Received on Monday, 18 March 2013 17:24:10 UTC

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